Distimo said that Google’s Android Market passed the 400,000 app mark at the start of the year, having reached 200,000 in April 2011 and 300,000 in August 2011.

Free content dominates the store, with more than two-thirds of the available apps falling into this category. The analytics firm noted that this has grown steadily from 60 percent in April 2011, driven by the increased popularity of the freemium business model.

The company noted that while Apple took 22 months to reach 200,000 apps and Android Market took 31 months, momentum then shifted in favour of the Google store – it took four months to pass 300,000 and four more to pass 400,000, compared with eight and seven for the iPhone store.

This echoes earlier reports of Google’s Android Market download performance. Again, while Apple had a head-start in the market, momentum shifted in favour of Android as the smartphone user base grew.

It was also noted that Android Market now has “almost more than 100,000 publishers active in its application store.” Developers publish 4.1 apps on average, down from nearly five twelve months ago.

Distimo noted that the recent milestone relates only to current applications in the store, and not those previously removed by Google or developers for various reasons.